Filtering The Confusion Out Of Sake Filtration

To Filter Is To Filter


A note from your translator Chris.

This article was originally written exclusively for a Japanese audience. In its original form, even when translated, it makes little sense to a non-Japanese speaker because the beginning of the article focuses on a purely language based issue. The writer is explaining about the different filtration processes that exists in Japanese. Now here comes the confusing part. In Japanese, two words are used to refer to the filtration stages in sake making: Kosu and Roka; the meaning of both is essentially filtration. However the former, Kosu, which is used to refer to the process of separating the lees from the liquid is not referred to as filtration in Japanese but pressing. To not refer to this process as filtration is not a mistake per se because what you are doing in effect is pressing the mash through a mesh, not filtering. If you want more of the rice sediment in the end product, you simply use a mesh with bigger holes so that more of the sediment passes through with the liquid. Yes, I know what you are thinking: “don’t be pedantic! this is actually filtering”. In the case of using a coarser mesh, the end result is of course what we lovingly refer to as cloudy sake. The rest of this article talks about the second type of filtration, the step that is referred to as filtration in Japanese as well: Roka. My translation starts from the part of the article that explains the Roka filtration process.
So one type of unfiltered sake is nigori (cloudy), or coarsely pressed sake. – See more at:

Roka Filtration (The Other Type Of Filtration)


Some of the freshly pressed type sakes are sold in their just pressed form with no other processing, but most of the time they go through an extra step of processing that removes any leftover rice sediment, yeast particles and solids: Oribiki.

And in some cases, the cut goes even deeper, removing even the very finite particles, off flavours and substances that are detrimental to the quality of sake. This is the process that is referred to as Roka filtration. At this point, the crucial difference between Kosu and Roka is probably clear.


There Are 2 Methods Of Roka Filtration


Incidentally, there are 2 main methods of Roka filtration. In the first, powdered active charcoal is poured into the sake before it is passed through a filter (this method is referred to as charcoal filtering, carbon filtering or active carbon filtering). The result of this type of filtering is clear sake devoid of excess off flavours or discoloration. The amount of charcoal used varies depending on the type of sake that is being made and the brewery. The second method, Suroka, passes the sake through the filter substituting charcoal for either diatomite, filter paper, a filter with a cartridge, or cotton instead.

MUROKA Unfiltered Type Sake.

In recent years, the word Muroka (unfiltered) has become prominent. While I think the meaning is of course pretty obvious to the consumer: sake which has not been filtered, it seems that it is interpreted different from brewery to brewery.


In order to explain how the two filtration processes Kosu and Roka differ, it was necessary to explain to you about Muroka as well.
Even top officials have tripped up over the definitions in the past. For example: there is the case of the North East tax office official who committed a fundamental blooper of saying that roka was not a type of filtration in sake making and instructed all the breweries in his constituency not to write Muroka on their bottle labels. If you are reading this article already well versed on its subject, then you are probably sniggering away right now, but if the difference is so confusing that even a top official can make such a mistake then your average user is surely going to be a little confused.

Some parts of sake are a little complicated; understanding them is surely the key to improving the taste experience.

Please acquire a little knowledge and enjoy your sake life.

Written by Omori Makoto – Sake Ambassador